Implement file preservation system for output directory cleaning

- Add sophisticated file preservation functionality to _clean_output_dir()
- Support .qsgen3_preserve file with shell glob patterns for selective preservation
- Preserve shared articles and important files during site regeneration
- Maintain backward compatibility (no preserve file = complete cleaning)
- Add comprehensive documentation in how-it-works.md
- Include example preserve file (.qsgen3_preserve.example)
- Remove legacy images directory and update documentation
- Fix workflow documentation formatting issues

bin/qsgen3

@@ -599,9 +599,102 @@ _minify_output_directory() {
 # --- Core Functions --- 
 _clean_output_dir() {
     _log INFO "Cleaning output directory: ${QSG_CONFIG[paths_output_dir]}"
-    # rm -rf "${QSG_CONFIG[paths_output_dir]}"/* # Be careful with this!
-    # For now, just ensure it exists
-    mkdir -p "${QSG_CONFIG[paths_output_dir]}"
+    
+    local output_dir="${QSG_CONFIG[paths_output_dir]}"
+    local preserve_file="$PROJECT_ROOT/.qsgen3_preserve"
+    
+    # If output directory doesn't exist, just create it
+    if [[ ! -d "$output_dir" ]]; then
+        mkdir -p "$output_dir"
+        if [[ $? -eq 0 ]]; then
+            _log DEBUG "Created output directory: $output_dir"
+        else
+            _log ERROR "Failed to create output directory: $output_dir"
+            return 1
+        fi
+        return 0
+    fi
+    
+    # Check if preserve file exists
+    if [[ -f "$preserve_file" ]]; then
+        _log INFO "Found preserve file: $preserve_file"
+        _log DEBUG "Performing selective cleaning with file preservation"
+        
+        # Create temporary directory to store preserved files
+        local temp_preserve_dir=$(mktemp -d)
+        local files_preserved=0
+        
+        # Read preserve patterns and backup matching files
+        while IFS= read -r pattern || [[ -n "$pattern" ]]; do
+            # Skip empty lines and comments
+            [[ -z "$pattern" || "$pattern" == \#* ]] && continue
+            
+            # Remove leading/trailing whitespace
+            pattern=$(echo "$pattern" | sed 's/^[[:space:]]*//;s/[[:space:]]*$//')
+            [[ -z "$pattern" ]] && continue
+            
+            _log DEBUG "Processing preserve pattern: $pattern"
+            
+            # Find files matching the pattern in output directory
+            while IFS= read -r -d '' file; do
+                if [[ -f "$file" ]]; then
+                    # Get relative path from output directory
+                    local rel_path="${file#$output_dir/}"
+                    local preserve_path="$temp_preserve_dir/$rel_path"
+                    
+                    # Create directory structure in temp location
+                    mkdir -p "$(dirname "$preserve_path")"
+                    
+                    # Copy file to preserve location
+                    if cp "$file" "$preserve_path"; then
+                        files_preserved=$((files_preserved + 1))
+                        _log DEBUG "Preserved file: $rel_path"
+                    else
+                        _log WARNING "Failed to preserve file: $rel_path"
+                    fi
+                fi
+            done < <(find "$output_dir" -name "$pattern" -type f -print0 2>/dev/null)
+            
+        done < "$preserve_file"
+        
+        # Remove the output directory
+        _log DEBUG "Removing output directory contents (preserving $files_preserved files)"
+        rm -rf "$output_dir"
+        
+        # Recreate output directory
+        mkdir -p "$output_dir"
+        if [[ $? -ne 0 ]]; then
+            _log ERROR "Failed to recreate output directory: $output_dir"
+            rm -rf "$temp_preserve_dir"
+            return 1
+        fi
+        
+        # Restore preserved files
+        if [[ $files_preserved -gt 0 ]]; then
+            _log DEBUG "Restoring $files_preserved preserved files"
+            if [[ -d "$temp_preserve_dir" ]]; then
+                # Copy preserved files back, maintaining directory structure
+                (cd "$temp_preserve_dir" && find . -type f -exec cp --parents {} "$output_dir/" \; 2>/dev/null)
+                _log INFO "Restored $files_preserved preserved files"
+            fi
+        fi
+        
+        # Clean up temporary directory
+        rm -rf "$temp_preserve_dir"
+        
+    else
+        # No preserve file - do complete cleaning as before
+        _log DEBUG "No preserve file found - performing complete cleaning"
+        rm -rf "$output_dir"
+        mkdir -p "$output_dir"
+        if [[ $? -ne 0 ]]; then
+            _log ERROR "Failed to recreate output directory: $output_dir"
+            return 1
+        fi
+    fi
+    
+    _log DEBUG "Output directory cleaning completed successfully"
+    return 0
 }
 
 _copy_static_files() {
@@ -1168,9 +1261,9 @@ _generate_rss_feed() {
             continue
         fi
 
-        local title=$(echo "$frontmatter" | grep -m1 -iE '^title:' | sed -E 's/^title:[[:space:]]*//i; s/^["\x27](.*)["\x27]$/\1/')
-        local date_iso=$(echo "$frontmatter" | grep -m1 -iE '^date:' | sed -E 's/^date:[[:space:]]*//i; s/^["\x27](.*)["\x27]$/\1/')
-        local summary=$(echo "$frontmatter" | grep -m1 -iE '^summary:' | sed -E 's/^summary:[[:space:]]*//i; s/^["\x27](.*)["\x27]$/\1/')
+        local title=$(echo "$frontmatter" | grep -m1 -iE '^title:' | sed -E 's/^title:[[:space:]]*//i; s/^[\"\x27](.*)[\"\x27]$/\1/')
+        local date_iso=$(echo "$frontmatter" | grep -m1 -iE '^date:' | sed -E 's/^date:[[:space:]]*//i; s/^[\"\x27](.*)[\"\x27]$/\1/')
+        local summary=$(echo "$frontmatter" | grep -m1 -iE '^summary:' | sed -E 's/^summary:[[:space:]]*//i; s/^[\"\x27](.*)[\"\x27]$/\1/')
         local draft=$(echo "$frontmatter" | grep -m1 -iE '^draft:' | sed -E 's/^draft:[[:space:]]*//i' | tr '[:upper:]' '[:lower:]')
 
         if [[ "$draft" == "true" && "${QSG_CONFIG[build_options_process_drafts]}" != "true" ]]; then